1. Field of the Invention
The present invention relates to a polypropylene resin composition having an excellent coating property after a plasma treatment, and an excellent weathering resistance, which is especially useful for a bumper.
2. Description of the Related Art
A polypropylene resin is widely utilized for automobile parts and various industrial parts, due to its excellent chemical properties, physical properties and moldability, and further, its light weight and relatively low cost. In particular, the use thereof for automobile bumpers is now widespread.
In general, automobile bumpers were used without a coating or when entirely coated, but a partially coated product, i.e., having a portion uncoated, has become popular from the viewpoint of the design demands, and accordingly, a weathering resistance in addition to an excellent coating property is now required of the polypropylene resin.
In general, a bumper made of a polypropylene resin was coated by the following method. Specifically, the surface of the bumper was washed with a halogenbased organic solvent and given a primer coating, and then a top coating was applied over the primer coating.
Currently, to reduce costs and improve productivity, a method is now widely used which comprises washing the surface of a bumper with a halogen-based organic solvent and subjecting the surface of the washed bumper to a plasma treatment, instead of applying the primer coating, and then applying a top coating over the plasma treated surface.
Nevertheless, when the bumper washed with an organic solvent is immediately placed in a plasma treatment tank, an organic solvent vapor volatilized from the surface of the bumper inhibits the generation of the plasma, and thus an effective plasma treatment cannot be conducted. Accordingly, the organic solvent present on the surface of the bumper is removed in a high temperature atmosphere, prior to the plasma treatment.
A polypropylene resin was blended with, for example, various antioxidants and light stabilizers, to enhance the weathering resistance and light stability thereof, but when such a polypropylene resin is molded into a bumper, washed with a solvent and dried in a high temperature atmosphere, these antioxidants and light stabilizers often bleed out onto the surface of the bumper during the above steps, and this brings a problem in that the plasma treatment of a bumper does not improve the coating property.